Brownification increases winter mortality in fish
(English)Manuscript (preprint) (Other academic)
In northernclimateswinter is a bottleneck for many organisms. Low light and resource availability constrain individual foraging rates,potentially leading tostarvation and increasedmortality.Increasinginput of humic substances to aquatic ecosystems causesbrownification of water and hence a further decreaseof light availability,which may lead tofurther decreased foraging ratesand starvation mortality during winter.To test this hypothesis, we measured the effectsof experimentally increased humicwaterinput on consumption and survival of young-of-the-year (YOY) three-spined stickleback (Gasterosteus aculeatus) over winterin largeoutdoor enclosures. Population densitieswereestimated in autumn andthefollowing springand food availabilityand consumptionwere monitoredoverwinter. As hypothesized,mortality washigher underhumic(76%)as compared to ambientconditions (64%).Also, body condition and ingested prey biomass werelower under humic conditionseven thoughresource availability wasnotlower under humic conditions. Light conditions were significantly poorer under humic conditions. This suggeststhat increased mortality and decreased body condition and ingested prey biomasswasnot due to decreased resource availability but due todecreasedsearch efficiencyin this visual feeding consumer. Increased future brownification of aquatic systems may therefore negatively affect both recruitment and densities of fish.
Brownification, winter mortality, light limitation, feeding efficiency, metabolism
IdentifiersURN: urn:nbn:se:umu:diva-127940OAI: oai:DiVA.org:umu-127940DiVA: diva2:1048333
FunderThe Kempe FoundationsSwedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 621-2011-3908Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE